PUB to survey Sungei Tampines and Sungei Api Api at Pasir Ris

PUB posted a quotation notice for a "Topographical Survey for Sungei Tampines and Sungei Api Api (Between Tampines Expressway and Pasir Ris Drive 3)" on 2 Mar 2012.

From the GeBiz website

The two Sungei are the blue ribbons on this map, Pasir Ris mangroves approximately where the red star is.

The notice was posted by an engineer from the PUB's Planning, Modelling & Water Quality of the Catchment and Waterways Department.

I wonder what this means for Sungei Tampines and Sungei Api Api and the Pasir Ris mangroves?